Laminar fluidic devices

ABSTRACT

Fluidic devices wherein the fluid stream or streams acting therein are always in the laminar state. The important elements of each fluidic device, which include one or more supply passageways, one or more receiver passageways, vents, a cavity and possibly one or more control passageways, are of a configuration and location such that fluid flowing through each supply passageway forms a laminar fluid stream which is capable of being received by one or more of the receiver passageways in a laminar state. The Reynolds number of the fluid forming the laminar fluid stream is preferably within the range of 200-1,500. The subject invention is applicable to a wide variety of fluidic devices including proportional and digital amplifiers, OR and AND gates, and rate sensors wherein the signal-to-noise ratio is substantially lower than that of conventional turbulent flow fluidic devices.

United States Patent Reader 1 541 LAMINAR FLUIDIC DEVICES [72] Inventor: Trevor D. Reader, King of Prussia, Pa. [73] Assignee: General Electric Company [22] Filed: Nov. 21, 1969 [2]] Appl. No.: 878,824

[ 51 May 16, 1972 Primary Examiner-Samuel Scott Attorney-Allen E. Amgott, Henry W. Kaufmann, William 0.

57 ABSTRACT Fluidic devices wherein the fluid stream or streams acting therein are always in the laminar state. The important elements of each flu'idic device, which include one or more supply passageways, one or more receiver passageways, vents, a cavity and possibly one or more control passageways, are of a configuration and location such that fluid flowing through each supply passageway forms a laminar fluid stream which is capable of being received by one or more of the receiver passageways in a laminar state. The Reynolds number of the fluid forming the laminar fluid stream is preferably within the range of ZOO-1,500. The subject invention is applicable to a wide variety of fluidic' devices including proportional and digital amplifiers, OR and AND gates, and rate sensors wherein the signal-to-noise ratio is substantially lower than that of conventional turbulent flow fluidic devices.

6 Claims, 9 Drawing Figures Patented May 16, 1972 3,662,772

3 SheetQ-Sheet l nvvnvrms: TREVOR 0. READER,

ATTORNEY Patented May 16, 1972 3,662,772

3 Sheets-Sheet 2 TREVOR 0. READER,

The subject invention generally relates to the area of fluidics and, in particular, to fluidic devices whichutilize a laminar flow stream.

Conventional state-of-the-art fluidic devices generallyutilize a turbulent (i.e., non-laminar) fluid streamflowingzfrom one or more supply passageways'to one or morereceiver passageways. Such a turbulent fluid stream may assume-asubstantially linear or vortical path. Fluidicdevices of this kind require a substantial pressure head of fluid andare inherently of very low efficiency with a low signal-to-noise ratio, due to the turbulence of the fluid stream. Turbulence amplifiers had been developed in which a laminar fluid stream is initially formed and flows from a supply passageway toward an aligned receiver passageway, andmea'ns are providedfor causingthe fluid stream to become turbulent in response to a'control signal. Turbulence amplifiers are characteristically slow in response time due to the recovery time necessary to'form a laminar fluid stream from a turbulent fluid stream once the control signals have been removed and also have a low signalto-noise ratio.

SUMMARY OF THE INVENTION Therefore it is an object of the subject invention to provide a fluid device utilizing and'maintaininga laminar fluid stream in the presence or absence of control signals.

Another object is to provide a fluidic device signal-to-noise ratio at high efficien'cy.

The above-stated objects are fulfilled in the subject invention by providing a laminar fluidic device comprised of at least one substantially linear supply passageway for forming a laminar fluid stream, the length of the supply passageway being at least ten times the smallest cross-sectional dimension of the nozzle portion of the supply passageway; at least one substantially linear receiver passageway capable of receiving at least a portion of the laminar fluid stream and having a cross-sectional area no less than that of the nozzle portion; a closed cavity between the supply and receiver passageways; and venting means in communication with the cavity and located adjacent to the receiver passageway for helping to maintain the fluid stream in the laminar state. Control means, such as control passageways located before the laminar fluid having a high stream enters the cavity, and wall means, located between the control means and the cavity for allowing wall attachment to take place, may also be provided. The subject invention may be used to provide a wide variety of laminar fluidic devices including, but not limited to, proportional and digital amplifiers, OR and AND gates and angular rate sensors.

The subject matter which is regarded as the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention, however, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic representation of a laminar fluidic proportional amplifier in accordance with the subject invention;

FIG. 2 is a crosssectional view of the device shown in FIG. taken along the line denoted lI-II;

FIG. 3 is a schematic view of a laminar fluidic digital amplifier in accordance with the subject invention;

FIG. 8-is a schematicrepresentation of a laminar-fluidic angular rate sensor in accordance with the subject invention; and.

FIG. 9 isa cross-sectional view of the device shown in'FlG. 8'taken along the line denoted lX-IX.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2 a schematic representation of alaminar fluidic proportional amplifier 10- is shown. Amplifier l0'is formed by a plurality of laminated plates l2, 14, 1.6, 18, Topand bottom plates 12, 20 are used as cover platesand 7 center plates-14, l6, 18 have had portions removedtherefrom is substantially linear inshape and should be of 'a. length at,

least ten times the smallest cross-sectional dimension of nozzle portion 24. The cross section of supply passageway 22. is preferably uniformalong its length and may be of any desirable shape such as circular, oval, rectangular or square. For purposes of illustration, the passageways shown in the figures are rectangular in cross section. For the embodimentsshown v in FIGS. 1 and 2' the smallest cross-sectional dimension of noz- FIG. 4 is a cross-sectional view of the device shown in FIG. 5

3 taken along the line denoted IV-IV;

FIG. 5 is a schematic view of another embodiment 'of laminar fluidic digital amplifier in accordance with the subject invention;

FIG. 6 is a schematic representation of a laminar fluidic OR gate in accordance with the subject invention;

FIG. 7 is a schematic representation of a laminar fluidic AND gate in accordance with the subject invention;

zle portion 24 would be the height of the passageway at that: point. If desired, passageway 22 may be slightly tapered.

Control passageways 38, 40 terminate adjacent the laminar fluid stream downstream of nozzle portion 24 and are preferably positioned upstream of the cavity so that the action of the control fluid in passageways 38, 40 on laminar fluid stream 42 serves only to deflect the stream and not to cause turbulence therein. The deflectionof fluid stream 42 by control fluid in passageways 38, 40 is controlled by the difference in pressures between the control fluids in the two control passageways with little if any mixing of the control fluids with the fluid of the laminar fluid stream. To best effect this, it is preferable that the height of the control passageways, be the same as the height of .the nozzle portion. Also, it is generally desirable, depending upon the pressures of the fluids involved, and the desired sensitivity, to have the width of each control passageway greater than the width of nozzle portion 24, for example 1 A 2 times as large. While each control passageway 38, 40 is shown to be at a right. angle to supply passageway 22, this angular relationship is not necessary.

Interaction cavity 26 is closed, that is, it is connected only to the supply and receiver passageways and the vents and in an indirect manner to the control passageways. The configuration of cavity 26 is such that the laminar fluid stream flows therethrough while remaining in the laminar state.

For proper operation of thesubject device, the fluid comprising fluid stream 42 should have a Reynolds number between 200 and 1,500 and the height of cavity 26 should eitherbe greater than ten times the height of nozzle portion 24. or it should be substantially the same height as that of nozzle portion 24. For cavity heights between one and ten nozzle heights the fluid stream has a tendency to attach itself to the top or bottom of the cavity, while for nozzle heights less than one nozzle height turbulence can occur at the step from the nozzle to the shallower cavity.

Two substantially linear receiver passageways 28, 30 are provided with a central vent passageway 34 located therebetween and vent passageways 32, 36 located on the other side of-each receiver passageways 28, 30, respectively. The three vent passageways make up the venting means for this embodiment with the central vent passageway 34 being substantially aligned with supply passageway 22. Generally it is desirable that the cross-sectional area of receiver passageways 28, 30 at their fluid input portion be at least as large as the cross-sectional area of nozzle portion 24, and preferably 1 /5 Ztimes as great. Receiver passageways 28, 30

are configured so that the laminar fluid stream 42 can flow therethrough with little impedance. It is therefore desirable that the passageways be either of substantially constant crosssection or slightly divergent,

Vent passageways 32, 34, 36 are of a configuration such that there is substantially no impedance to fluid flow therethrough to prevent disturbance of laminar fluid stream 42. It is undesirable for the vent passageways to either impede the flow of fluid or pull fluid therethrough as a result of venturi suction caused by an unrestricted diffusion in the vent. In effeet, the vent passageways should act as open windows. In order to maintain fluid stream 42 in laminar state, the venting means should be provided adjacent and as close as possible to the upstream portion of the receiver passageways.

The output of proportional amplifier is a pressure differential in the receiver passageways proportional to the difference in fluid pressures in control passageways 38, 40. In operation, a pressurized fluid with a Reynolds number less than 1,500 and preferably between 200 and 1,500 is supplied to supply passageway 22 to form laminar fluid stream 42. Control fluid, ducted to control passageways 38, 40 acts on laminar fluid stream 42 exiting from nozzle portion 24 to deflect that stream proportionally to the difference in pressures of the control fluid in the control passageways. If the pressures are equal, the stream will not be deflected and most of fluid stream 42 will enter central vent 34 with a substantially equal percentage of fluid entering receiver passageways 28 and 30, thereby providing a zero pressure differential output. If, for example, the pressure in control passageway 40 were greater than that in passageway 38, fluid stream 42 would be deflected so that a greater proportion of the fluid stream would exit through receiver passageway 28 than through passageway 30 thereby providing a pressure differential output proportional to the control pressure differential.

One way the gain of the proportional amplifier can be changed is by changing the length of interaction cavity 26. Generally, the longer the cavity, the higher the gain. It is generally desirable however, that the cavity be no longer than 50 times the smallest cross-sectional dimension of the nozzle portion, as the laminar fluid stream 42 begins to become marginally stable at greater lengths.

The embodiment shown in FIGS. 3 and 4 is one form of laminar fluidic digital amplifier. The structure shown is similar to that shown in FIGS. 1 and 2 with similar structured supply passageway 22, control passageways 38, 40 receiver passageways 28, 30 and vent passageways 32, 34 and 36. The major difference is that wall means 44 are provided between control passageways 38 and a cavity 46. Wall means 44, which includes two wall surfaces, defines, in part, a channel 48 having a height substantially equal to that of nozzle portion 24. Channel 48, at least a portion of which is divergent, has a minimum width no less than the width of the nozzle portion 24. The wall surfaces are positioned such that when the fluid stream becomes attached to one of wall surfaces 44, the fluid stream flows substantially directly through one of receiver passageways 28, 30 depending onto which wall surface it is attached.

In this embodiment cavity 46 is shown as having a height substantially equal to the height of nozzle portion 24. However, as explained above, a cavity having a height at least ten times as great as the height of nozzle portion 24 may also be used.

In operation, the digital amplifier shown in FIGS. 3 and 4 acts as a bi-stable device with fluid stream 42 being stable only when it is attached to one of wall surfaces 44. When the pressure of the control fluid in one os the control passageway, for example 40, is greater than the pressure in the other control passageway, fluid stream 42 is deflected so as to become attached, by the wall attachment effect, to a wall surface 44, in this example, the lower one, and exits primarily through one of the receiver passageways, in this example passageway 28. Fluid stream 42 remains this way until the pressure of the control fluid in the other control passageway, passageway 38, becomes sufficiently greater than the pressure in control passageway 40 to cause fluid stream 42 to be deflected away from the lower wall surface. Fluid stream 42 then becomes attached to the other wall surface 44, the upper one, and exits primarily through the other receiver passageway, passageway 30. Fluid stream 42 remains laminar throughout the operation of the device. Such a bi-stable device is commonly known as a flip-flop.

In FIG. 5 another embodiment of laminar fluidic digital amplifier is shown. The apparatus in FIG. 5 differs from that shown in FIG. 3 and 4 principally from the standpoint of the venting means used. In place of the central vent passageway, 34, the device of FIG. 5 uses a centrally located cusp 50 and a pair of vents 52, 54 located on opposite sides of interaction cavity 46. Cusp 50 is used to deflect fluid which is not able to enter one of receiver passageways 28, 30 to one of the vents 52, 54 without disturbing the laminar state of fluid stream. For example, if the laminar fluid stream is attached to the upper wall surface, the stream will be directed toward receiver passageway 28 with most of the fluid flowing therethrough. A small amount of the fluid stream including fluid from interaction cavity 46 which is entrained therein will exit through vent passageway 32 and a small amount will be deflected by cusp 50 and exit out through vent 54. Except for the venting, the operation of the device shown in FIG. 5 is exactly the same as the operation as the device shown in FIGS. 3 and 4.

In FIG. 6 a laminar fluidic OR gate is shown. In this device two substantially linear supply passageway 56, 58 angled in toward each other are provided. Each supply passageway 56, 58 has its own nozzle portion 60, 62, respectively, and bears the same dimensional relationship therewith as supply passageway 22, discussed above. The angle between supply passageways 56, 58 is preferably no greater than 45 to insure that the fluid streams flowing from the supply passageways remain laminar. One central receiver passageway 64 with two vent passageways 66, 68 adjacent thereto are provided. Cavity is located between the receiver and vent passageways and the supply passageways. The inlet of receiver passageway 64 is substantially aligned with both supply passageways 56, 58 so that when fluid flows through either or both supply passageways S6, 58 fluid flows out through receiver passageway 64 to provide a fluid pressure signal. In the embodiments shown, cavity 70 as well as all the passageways are shown to be of the same height, although cavity 70 may have a height at least ten times the height of nozzle portion 60, 62.

In FIG. 7 a laminar fluidic AND gate is shown which utilizes a structure similar to the OR gate structure in FIG. 6. Like the OR gate structure shown in FIG. 6, supply passageways 56', 58 should have an angle therebetween no greater than 45. The difference between the structure of the OR gate of FIG. 6 and the AND gate of FIG. 7 lies in the alignment of the receiver passageway 64 and vent passageways 66, 68 relative to supply passageways 56, 58. In the structure shown in FIG. 7 each supply passageway 56, 58 is aligned with a vent passageway 68, 66, respectively and receiver passageway 64 is aligned with a line substantially bisecting the angle between supply passageways 56' and 58'.

In operation, when fluid flows through either supply passageway 56 or 58, the laminar fluid stream formed thereby exits through vent passageway 68 or 67 with substantially no fluid flowing through receiver passageway 64. When fluid flows through both supply passageways 56', 58' both laminar fluid streams are deflected to form a single laminar fluid stream which flows through receiver passageway 64 thereby providing a fluid pressure indication of the presence of fluid flow in both supply passageways.

Both the OR gate and the AND gate of FIGS. 6 and 7 are passive devices in that the control fluid flow, which is the fluid flowing through the supply passageways, directly provide the fluidic operation; i.e., they do not act on a non-control fluid power stream.

In FIGS. 8 and 9 a laminar fluidic angular rate sensor is shown. The structure of the angular rate sensor is somewhat similar to that of the proportional amplifier shown in FIGS. 1 and 2, differing primarily in that no control passageways are provided. Supply passageway 22, cavity 26, receiver passageways 28, 30 and vent passageways 32, 34, 36 are all provided. The venting means for the angular rate sensor may also include additional vents 72, 74 which communicate with cavity 26 near nozzle portion 24. Supply passageway 22 is at least ten times as long as the smallest cross-sectional dimension of nozzle portion 24. Central vent passageway 34 is aligned with supply passageway 22 and receiver passageways 28, 30 are symetrically placed with respect thereto.

In operation a pressurized fluid is caused to flow through supply passageway 22 to form a laminar fluid stream. Like all the embodiments, in order to provide a fluid stream in a laminar state it is preferable that the fluid flowing through supply passageway 22 have a Reynolds number of between 200 and 1,500. As the angular rate sensor is rotated in a plane parallel to the plane of the surface shown in FIG. 8, laminar fluid stream 42 is deflected in a direction opposite to that of the rotation. For example, when the device is not being rotated, laminar fluid stream 42 will exit through central vent passageway 34 with a substantially equal, but small amount exiting through receivers 28 and 30 thereby producing a zero pressure differential between the two receiver passageways 28, 30. If the device is rotated in a clock-wise direction in the plane of the surface shown in FIG. 8, fluid stream 42 will be deflected so that more fluid enters receiver passageway 28 than enters receiver passageway 30 thereby providing a pressure differential between the two receiver passageways which is proportional to the angular rate of rotation of the device. Preferably receiver passageways 28, 30 are located such that when the device is being rotated at the maximum angular rate to be sensed, substantially all the fluid stream will enter one of the receiver passageways 28, 30 depending on the direction of the rotation. The use of the particular venting means shown helps to permit fluid stream 42 to remain in the laminar state even when the device is being rotated. Cavity 26 is shown as having a height at least ten times as great as the height of nozzle portion 24. Alternatively cavity 26 may be of substantially the same height as nozzle portion 24. The shapes of the cavities shown in the figures are merely representative of the shapes that may be used, subject to the height limitation discussed above. The shape of the cavity determines, at least in part, the venting means that should be used to maintain the fluid stream in the laminar state.

Many other embodiments and modifications, in addition to those discussed above, are intended to be included within the scope of the subject invention. For example, fluidic devices may be provided in accordance with said subject invention which are non-symetrical For example, a digital laminar device using only one of the wall surfaces shown in FIG. 3

might be provided. With wall attachment being effected only when the fluid stream is deflected in one direction. Also, the structure shown in FIG. 1 can be modified by eliminating vent passageways 32 and 36 and utilizing passageway 34 as a receiver passageway and passageways 28 and 30 as vent passageways to provide a laminar fluidic rectifier.

Additionally, the subject invention may beused in threedimensional fluidic devices wherein additional vents, receivers, and control passageways, as necessary would be provided.

Thus the subject invention provides a family of fluidic devices which are characterized by the use of a laminar fluid stream. The laminar fluid stream is provided by using a fluid having a Reynolds number less than 1,500 and preferably between 200 and 1,500 in a structure having at least one supply nozzle of a length at least ten times as great as the smallest cross-sectional dimension of the nozzle end of the supply passageway, at leastone linear receiver passageway having a cross-sectional area at least as great as the nozzle portion and venting means located adjacent the receiver passageway and being in communication with a cavity located between the supply and receiver passageways to maintain the fluid stream in a laminar state.

The scope of the subject invention is to be limited only by the appended claims. I

What I claim and desire to secure by Letters Patent in the United States is:

l. A laminar fluidic device for use with a fluid having a Reynolds number less than 1,500 comprising: 7

a. a substantially linear supply passageway having at its downstream end a nozzle portion for forming a laminar fluid stream, the length of said supply passageway being at least ten times the smallest cross-sectional dimension of said nozzle portion;

b. at least one substantially linear receiver passageway capable of receiving a portion of said laminar fluid stream from said supply passageway, the cross-sectional area of said receiver passageway being no less than the cross-sectional area of said nozzle portion;

c. a substantially closed cavity located between said supply and receiver passageways and through which said laminar fluid stream flows;

d. venting means in communication with said cavity and located adjacent to said receiver passageway for helping to maintain said fluid stream flowing through said cavity in the laminar state by presenting substantially no impedance to fluid flow therethrough; and

e. control means including atleast one control passageway located upstream of said cavity for acting on said laminar fluid stream formed in said supply passageway to control the deflection of said fluid stream, without causing turbulence therein, the width of the exit portion of said control passageway being at least one and one half times as great as the width of said nozzle portion.

2. A device as in claim 1 wherein the height of said cavity is substantially the same as the height of said nozzle portion.

3. A device as in claim 1 wherein the height of said cavity is at least ten times as great as the height of said nozzle portion.

4. A device as in claim 1 further including a second substantially linear receiver passageway, wherein a portion of said venting means is located between said two receiver passageways and is substantially aligned with said supply passageway.

5. A device as in claim 1 wherein the length of said cavity is no greater than fifty times the smallest cross-sectional dimension of said nozzle portion.

6. A device as in claim 5 further including wall means located between said control means and said cavity for providing at least one wall surface for attachment of said fluid stream, said wall means defining, in part, a fluid channel at least a portion of which is divergent, having a height substantially equal to that of said nozzle end and having a minimum width no less than the width of said nozzle portion.

n a a: 

1. A laminar fluidic device for use with a fluid having a Reynolds number less than 1,500 comprising: a. a substantially linear supply passageway having at its downstream end a nozzle portion for forming a laminar fluid stream, the length of said supply passageway being at least ten times the smallest cross-sectional dimension of said nozzle portion; b. at least one substantially linear receiver passageway capable of receiving a portion of said laminar fluid stream from said supply passageway, the cross-sectional area of said receiver passageway being no less than the cross-sectional area of said nozzle portion; c. a substantially closed cavity located between said supply and receiver passageways and through which said laminar fluid stream flows; d. venting means in communication with said cavity and located adjacent to said receiver passageway for helping to maintain said fluid stream flowing through said cavity in the laminar state by presenting substantially No impedance to fluid flow therethrough; and e. control means including at least one control passageway located upstream of said cavity for acting on said laminar fluid stream formed in said supply passageway to control the deflection of said fluid stream, without causing turbulence therein, the width of the exit portion of said control passageway being at least one and one half times as great as the width of said nozzle portion.
 2. A device as in claim 1 wherein the height of said cavity is substantially the same as the height of said nozzle portion.
 3. A device as in claim 1 wherein the height of said cavity is at least ten times as great as the height of said nozzle portion.
 4. A device as in claim 1 further including a second substantially linear receiver passageway, wherein a portion of said venting means is located between said two receiver passageways and is substantially aligned with said supply passageway.
 5. A device as in claim 1 wherein the length of said cavity is no greater than fifty times the smallest cross-sectional dimension of said nozzle portion.
 6. A device as in claim 5 further including wall means located between said control means and said cavity for providing at least one wall surface for attachment of said fluid stream, said wall means defining, in part, a fluid channel at least a portion of which is divergent, having a height substantially equal to that of said nozzle end and having a minimum width no less than the width of said nozzle portion. 